"When you submerge something in liquid, there is always a reaction. It’s a simple replacement of matter, buoyancy, which is expressed through Archimedes principle. Displacement occurs when an object is immersed in a fluid, pushing it out of the way.
However, bring a living organism into the equation and you have an entirely different situation. Sea creatures live and breathe in the water, but humans on the other hand, cannot survive underwater without oxygen. The average human being who is confident enough to enter the water, may immerse themself or merely ‘go for a dip.’ Surfers and divers have to adapt to this foreign habitat finding themselves in deeper more uncontrolled waters. When in these situations a number of physical, mental and emotional reactions occur."